DE102012215542A1 - Protective and / or diagnostic device for multi-voltage vehicle electrical system, multi-voltage vehicle electrical system and method for operating a multi-voltage vehicle electrical system - Google Patents

Abstract

A protection and / or diagnostic device (1) for a multi-voltage vehicle electrical system (10), the multi-voltage vehicle electrical system (10) having a first sub-network (11) which can be acted upon by a first voltage, and at least one further sub-network (12) with at least one further voltage being acted upon, wherein the first voltage is higher than the at least one further voltage, and wherein the first (11) and the at least one further subnetwork (12) have a common ground connection (GM), it is proposed wherein at least one further ground terminal (GG) is provided, are associated with the measuring means, which are adapted to measure a current flow through the at least one further ground terminal (GG), and diagnostic means (2) are provided, which are adapted for Basis of the measured current flow over the at least one further ground terminal (GG) as a function of at least one operating state of the multi-voltage On-board network (10) to diagnose a fault in the common ground terminal (GM) and / or the at least one further ground terminal (GG).

Description

The present invention relates to a protection and / or diagnostic device for a multi-voltage vehicle electrical system, a corresponding multi-voltage vehicle electrical system and a method for operating a multi-voltage vehicle electrical system according to the preambles of the independent claims.

State of the art

Multi-voltage electrical systems for motor vehicles are known in principle. They are used because due to the increasing number of electrical consumers in motor vehicles often a single power supply is no longer sufficient and / or consumers are used with different nominal voltages. Multi-voltage electrical systems typically have subnetworks with different voltage levels of, for example, 12 and 42V. It is also known to connect subnets via a DC-DC converter so that they can be powered by a common generator.

For the purposes of this application, predominantly two-voltage systems, ie multi-voltage vehicle systems with only two subnetworks of different voltage levels, are considered. However, as explained below, the invention is not limited to two-voltage electrical systems.

The subnets are often connected to a common ground wire. This can not be easily avoided in practice, as otherwise electrical machines, which have their ground connection via the housing and a mechanical connection via the internal combustion engine, would have to be insulated electrically against the internal combustion engine. However, such electrical insulation at a mechanically correspondingly heavily stressed point is associated with considerable effort, since the material properties of an insulating material are not always compatible with the mechanical requirements.

Due to the common ground connection, however, a problem arises when the common ground line is disturbed. In this case it may, as related below 1 explained, to reverse the polarity of electrical loads in a sub-network with lower voltage.

To protect against such reverse polarity beats the DE 199 61 622 A1 vor, in a two-voltage on-board network having two galvanically interconnected subnets of different voltage levels in which electrical loads are arranged to arrange a protective diode parallel to the electrical loads in the electrical system with the lower voltage.

As a result, the polarity reversal voltage of the electrical load is limited to the forward voltage of the diode at a ground fault. In the electrical system with the lower voltage, a fuse can be arranged, which is tuned to the maximum current of the diode. A similar solution using a protection diode is in the DE 101 38 477 A1 disclosed.

The WO 01/47084 A1 suggests using a voltage measuring device to detect overvoltage in a lower voltage subnet. If this detects an overvoltage, the relevant consumers are disconnected from the mains. The EP 1 453 171 A1 suggests appropriate switching means to protect consumers.

However, the measures known from the prior art often prove to be expensive and ineffective. There is therefore still the need for ways to reliably detect and / or prevent a reversal of consumers in the illustrated case.

Disclosure of the invention

Against this background, the present invention proposes a protective and / or diagnostic device for multi-voltage vehicle electrical system, a corresponding multi-voltage vehicle electrical system and a method for operating a corresponding multi-voltage vehicle electrical system having the features of the independent patent claims. Advantageous embodiments are the subject of the respective subclaims and the following description.

Advantages of the invention

With the proposed solution according to the invention can be in a corresponding multi-voltage electrical system with subnetworks of different voltage levels in a safe way reverse polarity of a subnetwork with lower voltage (hereinafter also referred to as "low-voltage network") recognize and / or prevent. For this purpose, in addition to a first, common ground connection additionally at least one further ground connection is provided, in particular in a sub-network of higher voltage (hereinafter also referred to as "high-voltage network"). A current flow is measured and diagnosed via this at least one further ground connection. The solution according to the invention is based on the recognition that, due to the parasitics in the respective components of the vehicle electrical system, the current flows via these ground connections are characteristic in two or more correspondingly mounted ground connections in different operating states of the on-board network and offer diagnostic possibilities.

In other words, the present invention proposes to provide at least one further, redundant ground connection, in particular in a sub-network of higher voltage. The attachment is preferably carried out on an existing component in the high-voltage network (hereinafter also referred to as "high-voltage component"). Advantageously, this component is a generator attached to an internal combustion engine of a motor vehicle, in particular a starter generator, which is conductively connected thereto, for example via a housing. However, as explained in more detail below, a connection can also be made directly to an internal combustion engine.

The at least one further ground connection is in this case equipped with a current estimating device (referred to in the context of this application as "measuring device"), which is set up to measure a current which flows via the at least one further ground connection and with an operating state, such as explained below, to make it plausible by means also provided diagnostic means. In this way, a demolition or other interruption already one of the ground connections can be seen and a reverse polarity of a vehicle electrical system can be reliably avoided.

By means of the measures proposed according to the invention, an alternative to an electrical insulation of corresponding high or low-voltage components relative to an internal combustion engine is provided. On electrical insulation at mechanically heavily stressed areas, which, as mentioned, often can only be done consuming, can therefore be dispensed with.

As already mentioned, the invention is based on the fact that characteristic power distribution patterns are formed in different operating states due to the parasitics in the components of the vehicle electrical system. Such current distribution patterns are particularly pronounced at high currents, so that a diagnosis according to the invention advantageously takes place in particular during starting processes of an internal combustion engine. This results in a considerable difference between a so-called cold start or first start and a so-called warm start. Details are in particular in connection with the 3 and 4 explained below.

The measures according to the invention can be used, in particular, in motor vehicles in which the starting of the internal combustion engine by means of a so-called pinion starter, ie a starter motor, which is connected to a low-voltage sub-network, the low-voltage network, takes place in the cold start. In the warm start of an internal combustion engine in such systems, however, takes place by means of a motor-driven starter generator in the high-voltage network.

In a particularly advantageous embodiment, it is provided that further ground connection and common ground connection are arranged in parallel so that when starting the engine with undisturbed common ground connection and undisturbed further ground connection, the currents flowing through the starter and starter currents flow through the common ground terminal and the other ground terminal.

In particular, it is advantageous that further ground connection and common ground connection are arranged in parallel in such a way that during cold start by means of the starter motor predominantly proportion of the occurring currents flows via the common ground connection, and the remaining, smaller proportion of the occurring currents via the further ground connection.

Furthermore or alternatively, it is advantageous that further ground connection and common ground connection are arranged in parallel in such a way that during warm start by means of the starter generator a predominant portion of the occurring currents flows via the further ground connection, and the remaining, smaller portion of the occurring currents via the common ground connection.

Advantageously, it can be provided to respectively determine corresponding currents in the control mode by a learning function for different operating states of the motor vehicle and, e.g. in diagnostic media. In other words, a protective and / or diagnostic device according to the invention will continuously measure and deposit currents in control mode. If the currents measured via the at least one further ground connection deviate from the stored currents, it can be assumed that at least one of the ground connections is disturbed. In this context, corresponding threshold values or tolerance ranges can be used.

Although the invention is described here predominantly with reference to vehicle electrical systems with two subnetworks, the finding according to the invention that characteristic power distribution patterns manifest themselves in different operating states due to the parasitic present in an electrical system at several ground connections, even in on-board networks with more than two subnets, so in general in multi-voltage on-board networks. The provision of several other ground connections is possible and useful, because in this way a redundant diagnosis is made possible.

An arithmetic unit according to the invention, for. As a control device of a motor vehicle is, in particular programmatically, adapted to perform a method according to the invention. In particular, the explained diagnostic means may be formed as part of a corresponding control device.

In a particularly advantageous aspect of the invention, the further ground connection is attached directly to the generator, and the explained diagnostic means are designed as part of a control of the generator, in particular integrated into the generator. This makes the wiring particularly easy.

In a particularly advantageous aspect of the invention, the further ground connection is directly attached to the starter generator, and the explained diagnostic means are designed as part of a control of the starter generator, in particular integrated into the starter generator. This makes the wiring particularly easy.

The implementation of the protection and / or diagnostic method in the form of software is also advantageous, since this causes particularly low costs, in particular if an executing control device is still used for further tasks and therefore exists anyway. Suitable data carriers for the provision of the computer program are in particular floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and the like. a. m. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described in detail below with reference to the drawing.

Brief description of the drawings

1 shows a two-voltage electrical system in the control and error mode in a highly schematic representation.

2 shows a two-voltage on-board network with a protection and / or diagnostic device according to a particularly preferred embodiment of the invention in a schematic representation.

3 shows current paths in a two-voltage electrical system according to a particularly preferred embodiment of the invention in the control and fault operation in a first operating state.

4 shows current paths in a two-voltage electrical system according to a particularly preferred embodiment of the invention in the control and fault operation in a second operating state.

5 illustrates parasitics in a two-voltage electrical system according to a particularly preferred embodiment of the invention in the form of a simplified equivalent circuit diagram.

Embodiment (s) of the invention

In 1 is a two-voltage electrical system shown very schematically and overall with 100 designated. It is a control mode with intact ground connection GM and a fault mode with disturbed, z. B. interrupted, ground terminal GM 'shown.

The two-voltage on-board network 10 has two subnets 11 . 12 of which a first subnetwork 11 the higher voltage subnet and another subnet 12 represents the subnet of low voltage.

The subnet 11 has a first energy storage B1, for example, a lithium-ion battery, a capacitive storage or a conventional vehicle battery, on. The first energy storage B1 provides, for example, a voltage of +48 V and is connected on the ground side to a common ground terminal GM. In the first subnet 11 is arranged by a simplified equivalent circuit symbolized first consumer V1. In a regular operation results in the first subnet 11 a regular current flow R1.

The further subnet 12 also includes an energy storage B2 and consumers V2 and V3. The energy store B2 can be designed like the above-described energy store B1 and supplies a lower voltage than this, for example a voltage of +12 V. In a regular operation results in the second subnet 11 a regular current flow R2.

If, as illustrated by the arrow denoted by GM ', an interruption of the ground connection to the common ground terminal GM, a fault current F flows, due to which in the other subnet 12 arranged loads V2 and V3 polarity reversed and be applied with a corresponding reverse polarity of 36 volts.

In 2 is a two-voltage on-board network with a protection and / or diagnostic device 1 represented according to a particularly preferred embodiment of the invention and in total also with 10 designated. The two-voltage on-board network 10 includes the components already associated with the 1 However, this is shown in an alternative representation.

In the two-voltage on-board network is in the first subnet 11 the first energy storage B1, as already in connection with the 1 explained, illustrated. The first energy storage B1 is switchable via switches SW1 and SW2 and connected to a ground terminal GB1. A second energy storage B2, as also explained above, is in the further subnetwork 12 provided and connected to a ground terminal GB2. The two-voltage electrical system comprises an internal combustion engine M, which is connected to a ground terminal GM. The ground connections GM, GB1 and GB2 are usually a common ground connection. With the internal combustion engine M, a generator G is connected, which is advantageously designed as a startable generator, ie as a motor-operated generator. The generator G is conductively connected to the engine M via a housing. The same applies to a starter motor S, for example in the form of a pinion starter, which is also conductively connected to the internal combustion engine M. The generator G and the starter motor S are, together with other components not shown, connected to the first B1 and second B2 energy storage.

According to the invention, a protection and / or diagnostic device 1 provided, the corresponding diagnostic or evaluation 2 may include. The diagnostic and evaluation means 2 can advantageously be provided in a control unit for the internal combustion engine M. The protection and diagnostic device 1 monitors a further ground connection GG, via which a current can be measured and made plausible in dependence on an operating state of the electrical system or of the motor vehicle. As a result, an interruption of one of the ground connections GG or GM can be detected and reverse polarity of the electrical system can be avoided.

3 shows a current path in a two-voltage electrical system according to a particularly preferred embodiment of the invention in a normal and fault operation in a first operating state, in this case at a cold start of the internal combustion engine M by means of the starter motor S. The 3 includes the essential components of 2 , which will not be explained again here.

In the 3 are fault currents with dashed arrows and regular currents, ie currents, as they occur in normal operation without broken ground lines, illustrated with solid arrows and with F (error) or R (rule). The thickness of the arrows corresponds to the order of magnitude of the respectively flowing current components or current intensities.

Due to the below related to 5 explained in more detail parasites in the components of the two-voltage electrical system 10 flows at start (by means of the starter motor S) of the internal combustion engine M in normal operation, ie undisturbed ground terminal GM, a predominant share (as illustrated by the thick solid arrows) of the currents occurring via the second energy storage B2, the starter motor S, an engine block of the internal combustion engine M and the common ground connection GM. A smaller proportion flows through the ground connection GG of the protection and diagnostic device 1 ,

In the event of a fault, which, as mentioned, is illustrated by dashed arrows, and in which the common ground connection GM is disturbed, a current flows from the second energy store B2 via the starter motor S, the internal combustion engine M, to the generator 1 and the ground connection GG.

Thus, when starting (by means of the starter motor S) of the internal combustion engine M, it can be established that there is a break in the ground connection of the internal combustion engine G when a correspondingly high current flows via the at least second ground terminal of the protective and diagnostic device. A corresponding evaluation device 2 can have threshold functions that define a maximum threshold for a "permissible" current via the further ground connection GG.

4 shows a current path in a two-voltage electrical system according to a particularly preferred embodiment of the invention in a normal and fault operation in a second operating state, in this case at a warm start of the internal combustion engine M by means of the (motor-driven) generator G. Again, the essential components correspond to those of 2 respectively. 3 why they are not explained again.

In the case of a warm start, an interruption in the connection via the further ground connection GG can be detected. In regular operation, also illustrated here with solid arrows of appropriate thickness, flows a majority of the current flows due to existing in the components of the electrical system parasitics on the common ground terminal GM and only a comparatively small share on the other ground terminal GG. In the event of a fault, in which there is an interruption in the further ground connection GG, the entire current flows via the common ground connection GM. A reduction of a current via the further ground connection GG compared to an "expected" value therefore allows a corresponding diagnosis of a fault in the further ground connection GG.

Overall, appropriate measures can thus be initiated in the event of an interruption or fault in either the common ground terminal GM or the further ground terminal GG, ie. H. For example, a first energy storage of higher voltage via switches SW1 and / or SW2 are disconnected from the electrical system to prevent a reverse polarity of the consumers V2 and V2 takes place in the low-voltage network.

As explained, the at least one further ground connection GG can be provided at different positions, as long as this ensures that corresponding characteristic current distribution patterns are formed. A further ground connection GG can also be provided on the internal combustion engine M if the measuring means are designed accordingly.

In the 5 is a purely exemplary two-voltage electrical system shown in the form of an equivalent circuit diagram. The specified inductances and resistances are summarized in the following table. In sum, they lead to the expression of the power distribution pattern explained above. element value explanation 101 1-5 μH Inductance (L) supply line 102 1 nH L screw connection (generator) 103 1 μH L mass (generator) 104 1 nH L engine block 105 200 nH L earth strap 106 1 nH L screw connection (starter motor) 107 1-5 μH L supply line (starter motor) 111 2-8 mΩ Resistance (R) supply line 112 250 μΩ R screw connection (generator) 113 2.51 mΩ R mass (generator) 114 10 μΩ R engine block 115 1.216 mΩ R mass band 116 250 μΩ R screw connection (starter motor) 117 2-8 mΩ R supply line (starter motor)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19961622 A1 [0006]
• DE 10138477 A1 [0007]
• WO 01/47084 A1 [0008]
• EP 1453171 A1 [0008]

Claims (17)

Protective and / or diagnostic device ( 1 ) for a multi-voltage vehicle electrical system ( 10 ) of a motor vehicle, the multi-voltage vehicle electrical system ( 10 ) a first subnetwork ( 11 ), which is acted upon by a first voltage, and at least one further subnetwork ( 12 ), which is acted upon by at least one further voltage, wherein the first voltage is higher than the at least one further voltage, and wherein the first ( 11 ) and the at least one further subnetwork ( 12 ) have a common ground terminal (GM), characterized in that at least one further ground terminal (GG) is provided, are associated with the measuring means, which are adapted to measure a current flow through the at least one further ground terminal (GG), and diagnostic means ( 2 ) are provided, which are set up on the basis of the measured current flow via the at least one further ground connection (GG) as a function of at least one operating state of the multi-voltage on-board network ( 10 ) to diagnose a fault in the common ground terminal (GM) and / or the at least one further ground terminal (GG). Protection and / or diagnostic device according to claim 1, characterized in that further ground connection (GG) and common ground connection (GM) are arranged in parallel such that when starting the internal combustion engine with undisturbed common ground connection (GM) and undisturbed further ground connection (GG) the currents flowing via a starter (S) and a generator (G) flow via the common ground connection (GM) and the further ground connection (GG). Protection and / or diagnostic device according to claim 1 or 2, characterized in that further ground terminal (GG) and common ground terminal (GM) are arranged in parallel so that at cold start by means of the starter (S), a predominant portion of the currents occurring over the Common ground (GM) flows, and the remaining, smaller proportion of the currents occurring via the further ground terminal (GG). Protection and / or diagnostic device according to claim 1 or 2 or 3, characterized in that the generator (G) is designed as a starter generator, and that further ground terminal (GG) and common ground terminal (GM) are arranged in parallel, that during warm start by means of Starter generator (G), a predominant proportion of the currents occurring via the further ground terminal (GG) flows, and the remaining, smaller proportion of the currents occurring via the common ground terminal (GM). Protective and / or diagnostic device ( 1 ) according to one of Claims 1 to 4, in which the common ground connection (GM) is provided on an internal combustion engine (M) of the motor vehicle, with which at least some components (V1, V2, V3, G, S) of the first (GM) 11 ) and the at least one other ( 12 ) Subnet are masseseitig connected. Protective and / or diagnostic device ( 1 ) according to any one of claims 1 to 5, wherein the at least one further ground connection (GG) is a ground connection of a generator (G) which is conductively connected to the internal combustion engine (M). Protective and / or diagnostic device ( 1 ) according to one of the preceding claims, wherein the first voltage is 48 V and the at least one further voltage is 12 V or 14 V. Protective and / or diagnostic device ( 1 ) according to one of the preceding claims, in which the first subnetwork ( 11 ) by means of at least one voltage source (B1, G) with the first voltage and the at least one further subnet ( 12 ) can be acted upon by at least one further voltage source (B2) with the at least one further voltage. Multi-voltage electrical system ( 10 ) for a motor vehicle having a first subnetwork ( 11 ), which is acted upon by a first voltage, and at least one further subnetwork ( 12 ), which is acted upon by at least one further voltage, wherein the first voltage is higher than the at least one further voltage, and wherein the first ( 11 ) and the at least one further subnetwork ( 12 ) have a common ground connection (GM), characterized by a protection and / or diagnostic device ( 1 ) according to any one of the preceding claims. Method for operating a multi-voltage vehicle electrical system ( 10 ) or a protective and / or diagnostic device ( 1 ) according to one of the preceding claims, characterized in that by means of the at least one further ground terminal (GG) associated measuring means at least temporarily a current flow over the at least one further ground terminal (GG) is measured and the diagnostic means ( 2 ) on Basis of the measured current flow over the at least one further ground terminal (GG) as a function of at least one operating state of the multi-voltage vehicle electrical system ( 10 ) diagnose a fault in the common ground terminal (GM) and / or in the at least one further ground terminal (GG). Method according to Claim 10, in which the at least one operating state of the multi-voltage on-board electrical system ( 10 ) comprises at least a cold start and a warm start. Method according to claim 10 or 11, in which a fault in the common ground connection (GM) is diagnosed by determining that the current flow measured via the at least one further ground connection (GG) corresponds to one in the at least one operating state of the multi-voltage on-board network (GM). 10 ) does not correspond to the expected current flow. A method according to claim 12, characterized in that during a cold start, the fault in the common ground terminal (GM) is diagnosed when the measured over the at least one further ground terminal (GG) current flow exceeds a maximum threshold. A method according to claim 10, characterized in that at a warm start, the fault in the at least one further ground terminal (GG) diagnosed by that it is determined that exceeds the measured via the at least one common ground terminal (GM) current flow exceeds a maximum threshold. Method according to Claim 12, in which the expected current flow is determined in each case on the basis of the components (V1, V2, V3, G, S) of the multi-voltage on-board electrical system ( 10 ) is determined. Arithmetic unit which is adapted to perform a method according to any one of the preceding claims 10 to 15. A computer program having program code means stored on a computer-readable medium which cause a computer or corresponding computing unit to perform a method according to any one of claims 10 to 15 when executed on the computer or the corresponding computing unit of claim 11.

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